Daniel W.H. Su, Sr. geomechanical engineer Greg J. Hasenfus, Sr. geomechanical engineer Luke Stull, geologist Jun Lu, geomechanical engineer Mark Van Dyke, geologist Stephen Morgan, geologist Paul Kelley, mine engineer Don Teter, project engineer

Outline Introduction Objective Geology/Geologic Reconnaissance Hydro Frac Hole Locations and Frac Process Flac3D Models Longwall Visual Analysis (LVA) Monitoring Face Monitoring and Evaluation Conclusions

Introduction

Sandstone Intrusion Encountered During Development

Introduction Sandstone Intrusion Encountered During Development Base of Sandstone Channel

Introduction F20 Longwall Panel Problems Delayed caving behind shield supports Massive sandstone pot-outs in front of shields Increased risk to personnel Delayed Production Longwall production footage per week

Objective To evaluate the effectiveness of the hydraulic fracturing program and the validity of Longwall Visual Analysis (LVA) software to mitigate the impact of a 1, 000-foot (305-meter) wide massive sandstone channel on a 1,500-ft-wide (457-meter-wide) longwall face.

Geologic Reconnaissance  In-Mine Core Drilling  Stratascope Observations  In-Mine Mapping  Primary Stress Orientation  Rock Lab Testing Average Axial Compressive Strength 8283 psi

Geologic Reconnaissance Trough of Sandstone Channel at Wall # 29 Base of Sandstone INBY OUTBY WALL #33 WALL #27 Drawslate Pittsburgh Seam 5 Feet Vertical Scale

Frac Hole Locations and Frac Stage Horizons

Frac Process Perforations were shot into the casing at the targeted horizons to pre- fracture the sandstone. The estimated shot penetration into the borehole surface was about 26 to 30 inches (0.66 to 0.76 meter).

Frac Process Water fracing was employed

Frac Process Fracing result Initial break Shut-in

Outline Introduction Objective Geology/Geologic Reconnaissance Hydro Frac Hole Locations and Frac Process Flac3D Models Longwall Visual Analysis (LVA) Monitoring Face Monitoring and Evaluation Conclusions

Flac3D Model Without Frac Massive Sandstone Clayey Shale Longwall face Massive Sandstone Clayey Shale Longwall face Shear stress, psi With Frac Frac horizon 15 ft

Longwall Visual Analysis (LVA) LVA was installed to track the face pressure and cavity formation index. Cavity Risk Index (CRI)

Face Monitoring and Evaluation To evaluate the effectiveness of the hydraulic fracturing program and the validity of LVA software, daily face monitoring over a 4-week period was conducted. Based on the collected information, the correlations among the observed face conditions, the hydro frac hole locations and the LVA cavity formation prediction were analyzed. Underground Observation Hydraulic Fracturing Longwall Visual Analysis

Ming Direction

Dec. 20, 2011

Face Monitoring and Evaluation

Longwall production footage per week F21—SS fraced F20—SS not fraced

Conclusions  Successful application of hydraulic fracturing technique.  Successful application of LVA software.  Improve safety and increase productivity.

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